Method and apparatus for providing GPS pseudorange correction and carrier
phase correction information for navigation or surveying activities over
a selected geographic region S of arbitrary size. In a navigation mode, a
virtual reference station (VRS), positioned near a selected location L,
receives differential GPS (DGPS) correction signals, translates these
signals into a selected format, and broadcasts this DGPS information in
this format for use by a local user. In a survey mode, the VRS receives
corrected GPS information, translates this information into a selected
format and broadcasts this translated and corrected GPS information and
the VRS location, for use by a mobile station in forming a baseline
vector from the GPS mobile station to the VRS location.